(a). Field of the Invention
The present invention relates to a method and an apparatus for emulating audio effect, more particularly, to a method and an apparatus that applies an architecture capable of using echo, reverberation and direct sound simultaneously.
(b). Description of the Prior Arts
When sound is produced in an enclosed space, multiple reflections will build up and blend together creating so-called “audio effects”. For instance, when a short sound impulse is created by a person inside a valley, a reflected sound wave with a lower intensity will bounce back to the person's ear a little later, since the energy of the sound wave will decay during traveling and the walls or other surfaces in the valley will also absorb some of the sound energy while reflecting the sound wave, such that the distinct series of delayed and attenuated sound waves is what we call echoes.
If a continuous sound is created, instead of the short sound impulse, the continuous sound will not only be reflected in the valley, but also the reflected sounds of the continuous sound will superimpose on each other and eventually reach a steady state in very short period of time (about a few seconds). Furthermore, when the continuous sound stops, the reflected sounds can still be heard for a period of time, and the reflected sounds heard by the person during the period of time is what we call reverberation.
Hence, the echoes and the reverberation heard in the valley are the “audio effects” resulting from the sound wave reflecting in the valley.
Following the coming of digital era, audio effects of a sound wave in a certain environment can be emulated by using only a few simple electronic devices. Please refer to FIG. 1, which is a schematic illustration depicting an echo emulation apparatus of prior arts.
As seen in FIG. 1, the echo emulation device 100 is mainly composed of a delay unit 110 and an adder 120. Wherein, an audio source signal 105 emerging at t1 time is transmitted dividedly that one is forwarded directly to the adder 120 and the other is diverted to the delay unit 110 for delaying the signal 105 for a Δt time before it reaches the adder 120, thereafter, the two signals are synthesized using the adder 110 such that an echo signal 130 is outputted from the adder 120. In this regard, the echo signal is the combination of the audio source signal 105 emerging at t1 time and the audio source signal 105 which has been delayed for a Δt period (that is, emerging at t2).
Please refer to FIG. 2, which is a schematic illustration showing a reverberation emulation device of prior arts. As seen in FIG. 2, the reverberation emulation device 200 is composed of a delay unit 110, an adder 120 and a gain unit 205. Wherein, the audio source signal 120 emerging at t1 is first fed into and then outputted from the adder 120, afterward, the signal outputted from the adder 120 is fed back to the adder 120 for synthesizing with the audio source signal 105 after it had been delayed for a Δt period by the delay unit 110 and been decayed by the gain unit 205, thereafter, the adder outputs the synthesized signal, moreover, the process is repetitious for creating a reverberation effect.
In this regard, the final reverberation signal 210 outputted from the reverberation emulation device 200 will be a combination of the audio source signal 105 emerging at time t1 and all the audio source signals 105 which have been successively decayed and delayed by a period of Δt (i.e. at time t2, t3, . . . etc.).
In addition to echo and reverberation, there are many more audio effects that can be simulated using electronic devices of different configurations. However, how to achieve a better and more diversified audio effect using limited funding (i.e. the longer the delay time needed by the audio source signal, the larger the memory will be needed, and consequently, the delay device will be more expensive) and limited available combination of electronic devices are the issues worth considering.
Thus, the present invention comes up with an apparatus and method for emulating audio effects, which is capable of achieving best and most diversified audio effects using efficiently composed electronic devices and limited funding.